The present invention relates to coupling members for coupling an optical system to an endoscope shaft, of the kind comprising a locking ring whose proximal terminal surface has an excision through which may pass an annular collar of the optical system insertible into the shaft, and a radial guiding stud which engages in a groove or slot of the shaft provided with an inclination and which, by twisting out of the insertion position of the optical system couples the latter to the endoscope shaft in the manner of a bayonet joint. Hereinafter such a coupling member will be referred to as "of the kind described".
Commonly known coupling members of the kind described may be released in particular circumstances during manipulation of the endoscope by accidental twisting of the locking ring, or the turning of the locking ring into the coupled position may have been omitted by inadvertence. The risk then arises that the costly optical system may slide out of the shaft and may in particular circumstances be destroyed or damaged by dropping on to the floor.
It is an object of the invention to provide a construction in which the locking ring is always brought into its coupling position and is secured against accidental twisting in the direction causing disengagement of the coupling.